1. Field of the Invention
The present invention relates to an apparatus for applying a liquid agent (such as photoresist and passivation) on a surface of a substrate (such as a semiconductor substrate, a ceramic substrate, a glass substrate or the like) while supporting the substrate by a spinchuck and while rotating the spinchuck in a cup which prevents the liquid agent from scattering. In particular, the present invention relates to an apparatus in which liquid agent which would otherwise adhere to the inside of the circumferential wall of the cup or to a member for regulating air flow in the cup can be efficiently rinsed.
2. Description of the Related Art
An apparatus of this kind is generally referred to as a "spinner". A spinner, as is well-known in the art, is used in a photoresist applying process, a developing process, an etching process and the like.
In the above described processes, when the liquid agent is applied to a rotating substrate, the liquid agent tends to adhere to the inside of a circumferential wall of the cup, to a member for regulating air flow in the cup and to other members. When the liquid agent adhering to the inside of the circumferential wall dries out and cakes, it changes into fine powder dust and scatters in the cup due to vibration of the rotating substrate, or the like. The scattered dust adheres to a surface of the substrate being processed, and thereby reduces production yield.
A spinner which is disclosed in Japanese Utility Model Application Laid Open No. 58-40275 is designed to eliminate the above-described disadvantage. Referring to FIGS. 1 and 2, the apparatus includes a cup 101 for preventing treatment solution from scattering and a spinchuck 110 provided at the center of the cup 101 for supporting a substrate W and for rotating the same. The cup 101 surrounds the spinchuck 110 and includes a circumferential wall 103 for preventing the treatment solution from scattering. A bottom wall 105 is located below the spinchuck 110 for receiving the dropping treatment solution.
The bottom wall 105 includes a ring-shaped bottom plate 106 protruding toward the center of the bottom wall 105 and a slant bottom surface 107 for catching the dropping treatment solution and for letting the same flow in the direction of the bottom plate 106. The bottom plate 106 has a ventilation duct 118 and a drain 119 for waste liquid. The slant bottom portion 107 is horn-shaped with a slant surface 116. A peripheral portion of the bottom portion 107 is connected to the bottom plate 106. The central portion of the bottom portion 107 is located near the top of the spinchuck 110.
The apparatus further includes a ring-shaped rinse agent conduit 117 provided around an upper edge portion of the slant bottom portion 107 for supplying rinse agent on the slant surface 116, and a ring-shaped rinse agent conduit 104 provided on an inner surface of an upper portion of the circumferential wall 103 for supplying the rinse agent on the inner surface of the circumferential wall 103.
In operation, the substrate W is fed to the spinchuck 110 by a substrate transporter (not shown) and is supported on the spinchuck 110 by vacuum suction or the like. After a nozzle (not illustrated) supplies photoresist to an upper surface of the substrate W, the spinchuck 110 is rotated by a motor (not illustrated) at a high speed. Excess photoresist is scattered around the substrate W by centrifugal force such that a uniform photoresist layer is formed on the upper surface of the substrate W.
The photoresist scattered around the substrate W adheres to the inner surface of the circumferential wall 103, to the slant surface 116 and the like. The conduit 104 supplies organic solvent to the inner surface 108 of the circumferential wall 103. The photoresist dissolves in the organic solvent and goes down toward the bottom plate 106 along the inner surface of the circumferential wall 103.
The conduit 117 supplies the organic solvent to the slant surface 116 of the slant bottom portion 107. Photoresist adhering to the slant surface 116 dissolves in the organic solvent and flows down the slant surface 116 toward the bottom plate 106.
A slope is formed on the upper surface of the bottom plate 106 for flowing waste liquid toward the drain 119. The waste liquid flows to the drain 119, from which it is externally discharged.
The air in the apparatus is forcibly discharged from the ventilation duct 118 to the outside.
The organic solvent is continuously supplied to the inner surface 108 of the circumferential wall 103 and the slant surface 116 through the rinse agent conduits 104 and 117, thereby preventing the photoresist from adhering to the inner surface 108 and the slant surface 116. Thus, the photoresist cannot dry to the surfaces 108 and 116, turn into fine dust and scatter around in the cup to adhere to the substrate W.
However, the conventional apparatus cannot completely eliminate the disadvantages of the prior art. Namely, the rinse agent is not supplied around the conduits 104 and 117. As a result, liquid agent adhering to the conduits 104 and 117 is never rinsed therefrom. The liquid agent adhering to the conduits 104 and 117 soon dries out and turns into powder, which is scattered in the cup and adheres to the substrate W. If this disadvantage were overcome, production yield would be improved.